Journal of Applied Pharmaceutical Science Vol. 10(12 ), pp 029-034, December, 2020 Available online at http://www.japsonline.com DOI: 10.7324/JAPS.2020.101204 ISSN 2231-3354
The new two-dimensional light scattering method for recognition of pharmaceutical enantiomers
Anton Vladimirovich Syroeshkin, Olga Valerievna Levitskaya*, Tatiana Vadimovna Pleteneva, Elena Valerievna Uspenskaya, Maria Antonovna Tribot-Laspiere, Irina Vladimirovna Tarabrina Department of Pharmaceutical Toxicological Chemistry, Medical Institute, Peoples Friendship University of Russia (RUDN University), Moscow, Russian Federation.
ARTICLE INFO ABSTRACT Received on: 12/08/2020 The results of applying the developed mathematical model of the folding of two-dimensional light scattering (2D-LS) Accepted on: 23/10/2020 patterns into a descriptor to identify the enantiomers of optically active pharmaceutical substances are presented in the Available online: 05/12/2020 article. The following pharmaceutical substances were a subject of this research: L-valine, D-valine, racemic mixture L, D-valine, L-glucose, D-glucose, and L-ascorbic acid. A digital microscope with high spectral density was used to obtain instant 2D-LS patterns. The obtained data were mathematically processed using the original computer program Key words: “Vidan”, which uses a mathematical model for the folding of the 2D-LS pattern into descriptors, which are analogs Distinction of optical of topological indices in quantitative structure-activity correlations approaches to drug analysis. The 10 descriptors antipodes, two-dimensional were used as criteria for the difference in the 2D distribution of the scattered light intensity. The use of mono- and light scattering, valine, multidescriptor analyses allowed us to determine the authenticity of pharmaceutical substances of different classes and glucose. their optical isomers. It was found that the dispersion of crystalline substances of optical antipodes up to submicron size led to the leveling of light scattering patterns. The mathematical model was developed and applied for the folding of 2D-LS diagrams into a descriptor. This allowed us to identify the optical antipodes of pharmaceutical substances.
INTRODUCTION new drug. Reducing the development time of a chiral drug largely About 40% of finished dosage forms contain chiral depends on the efficiency of determining the absolute configuration pharmaceutical substances, and only a quarter of them are and the enantiomeric purity of a substance (Calcaterra and individual enantiomers (Calcaterra and D’Acquarica, 2018). As a D’Acquarica, 2018). In scientific research and the pharmaceutical rule, the pharmacological activity of chiral substances is limited industry, the X-ray crystallography, nuclear magnetic resonance, by one of the enantiomers – the eutomer. In some cases, the enantioselective chromatography, vibrational circular dichroism, inactive enantiomer (distomer) can cause unwanted side reactions and polarimetry are used for the recognition and separation and even toxicity. The ballast nontoxic enantiomer that undergoes of enantiomers (Sangamithra et al., 2019). It was proposed to biotransformation exerts an additional burden on the body. create the tool kit “Chiral Technology” as a set of methods for The pharmacy domain that has been actively determining the absolute stereochemistry and enantioseparation developed during the last decade is associated with the creation of chiral molecules (McConnell et al., 2007). The need for pure of enantioselective drugs from already already known racemic enantiomers requires the selection of the most cost-effective substances (Challener, 2016; McConnell et al., 2007). This so- method of analysis, as well as the expansion of the bank of chiral called “chiral switching” allows the eutomer to be registered as a instruments (Challener, 2016). The search for new reliable systems for the recognition of optical isomers is expanding. It should be directed toward methods of identification without destruction and preliminary sample preparation of a pharmaceutical substance. *Corresponding Author These criteria are met by the method of two-dimensional Olga Valerievna Levitskaya, Department of Pharmaceutical & Toxicological dynamic light scattering (2D-LS) using the developed device and Chemistry, Medical Institute, Peoples' Friendship University of Russia (RUDN original software (Lesnikov et al., 2016). University), Moscow, Russian Federation. E-mail: levitskayavolha @ gmail.com
© 2020 Anton Vladimirovich Syroeshkin et al. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). 030 Syroeshkin et al. / Journal of Applied Pharmaceutical Science 10 (12); 2020: 029-034
The method has successfully proven itself in assessing The distributions by volume and number fractions (“size the quality of liquid dosage forms: suspensions, emulsions, spectra”) of D-glucose substance had one maximum at 100 µm, tinctures, and determining the authenticity of medicinal and while L-glucose is characterized by the existence of three maxima table waters without opening the package, as well as the stability at 10, 40, and 70 µm. After the dispersion, the particle sizes were of cluster structures in waters of different isotopic composition in the submicron range. (Bunkin et al., 2018; Goncharuk et al., 2011; Karpov et al., A digital microscope (Levenhuk DTX 30) with high 2011; Koldina et al., 2019; Ul'yantsev et al., 2009). Reliability spectral density LEDs (Light-Emitting Diode) and a video camera of measurements, nondestructive nature, low cost, simplicity of connected to a personal computer was used to register instant 2D- calibration procedures, and short measurement times are important LS. The measurements were carried out every second during 120 advantages of the method in the analysis of pharmaceutical seconds and were repeated six times (n = 720). The data obtained substances. were mathematically processed using the original computer This work presents the results of applying the method program “Vidan” (Certificate No. 2005612135). The program of 2D-LS for the recognition of the antipodes of optically processes a mathematical model for folding a 2D-LS pattern into active pharmaceutical substances without preliminary sample descriptors that are analogs of topological indices in the method preparation. of quantitative structure-activity correlations (Sprous et al., 2010). The following 10 descriptors were used as criteria for the MATERIALS AND METHODS difference in the 2D distribution of the scattered light intensity: d1, The following pharmaceutical substances were a subject d2, d3, standard deviation (SD)(d1), SD(d2), SD(d3), R1, R2, R3, and of research: L-valine (≥ 98% for HPLC (High Performance Liquid r (Koldina et al., 2019). The measurement results made it possible Chromatography), V0500), D-valine (≥ 98%, 855,987), racemic to reveal differences in the nature of the studied samples. mixture L, D-valine (≥ 99.0%, 94,640), L-glucose (≥ 99 %, G5500), D-glucose (≥ 99.5%, G8270), L-ascorbic acid (≥ 99.0%, A5960). All RESULTS AND DISCUSSION substances were obtained from Sigma-Aldrich (Saint Louis, MO). The surface of pharmaceutical substances is a unique Dispersion of substances was carried out by grinding in characteristic and its properties depend on the chemical nature a mechanical cutting knife mill (F-306, HT Machinery, Japan) by of the analyzed object and the features of the synthesis. The means of free, direct impact (according to Rumpf) for 20 minutes possibility of describing the frequency and amplitude of surface in a pulse mode (Uspenskaya et al., 2020). The particle size microvibrations opens prospects for determining the authenticity distribution of glucose enantiomers (before and after dispersion) of a substance up to the assessment of the authenticity of optical was recorded by low-angle laser light scattering on a Malvern antipodes and their racemates. 3,600 particle counter. The radiation source was a low-power The integral characteristics of the 2D-LS pattern can helium-neon laser emitting monochromatic light (λ = 633 nm). be represented in different ways. The primary values of the i-th The measurements were carried out with stirring by placing the descriptor on time can be used to calculate the SD and plot the substances in an inert solvent (n-hexane). The distribution of the dependence of the average SD of the i-th descriptor on its value proportion (%) of particles of a given size from the total number SD(di) = F(di). In addition, it is possible to plot the spectra of was presented in the range 1–120 μm (Fig. 1). relative frequency (RF) of descriptors in coordinates “di – RF
(di).” As an example of using the listed mathematical processing
methods of light scattering patterns by the first descriptord ( 1), the substances of L-ascorbic acid, L-valine, and L-glucose are considered (Fig. 2). As a consequence, it is easy to identify pharmaceutical substances within the framework of the chosen
mathematical model. For the function RF(d1) = F(d1), a set of characteristics such as the position of the maxima, their width, and shape can be used as criteria for authenticity. The use of mechanochemical treatment of substances in the pharmaceutical industry to increase their biological activity requires new approaches to assessing their quality (Syroeshkin et al., 2019). It was found that the dispersion of enantiomeric substances led to a change in the dynamic light scattering patterns. Thus, the identification of glucose enantiomers after
dispersion becomes impossible since the RF spectra RF(d1) =
F(d1) are superimposed on each other. At the same time, native substances occupy separate areas in the range of values of the selected descriptor and can be easily identified Fig. ( 3). The absence of differences in the RF of the descriptor for the substances of the D- and L-glucose optical isomers subjected to dispersion correlates with the results obtained using a low-angle Figure 1. Particle size distribution of glucose optical isomers before and after laser dispersion meter (see Fig. 1). The absence of particles in dispersion (m = 0.03 g; V = 3 ml; stirring; solvent n-hexane). the micrometer range is accompanied by the disappearance of Syroeshkin et al. / Journal of Applied Pharmaceutical Science 10 (12); 2020: 029-034 031
Figure 2. Evaluation of light scattering patterns of pharmaceutical substances in the form of functions: (A) d1 = F(t); (B) SD(d1) = F(d1);
(C) RF(d1) = F(d1), the relative frequency of the descriptor d1. L-ascorbic acid (a), L-valine (b), and L-glucose (c). n = 720.
Figure 3. 2D-LS diagrams of glucose enantiomers substances before (A) and after (B) dispersion. n = 720.
differences in the characteristics of dynamic light scattering. Thus, SD(d1) = F(d1)), made it possible to identify three substances: light scattering by particles with a diameter of less than 1 micron racemic valine and its optical antipodes, D-valine, and L-valine. does not depend on the nature of the substance. Similar patterns It should be emphasized that the identified substances are were observed for valine (Fig. 4). chemically indistinguishable, but the peculiarities of their Changes in the light scattering on the time of the spatial structure are the basis for the observed specificity of sample surfaces, described using the descriptors d1 = F(t) and dynamic light scattering. All characteristics selected within the 032 Syroeshkin et al. / Journal of Applied Pharmaceutical Science 10 (12); 2020: 029-034
Figure 4. 2D-LS diagrams of the valine optical antipodes and racemic mixture before (A) and after (B) dispersion: a – d1 = F(t); b – SD(d1) = F(d1), c – RF(d1) = F(d1), and n = 720. mathematical model framework demonstrated the possibility differences, which was reflected in the formation of a common of identifying both enantiomers and racemate. At the same range of the descriptor values d1, SD(d1), and overlapping of the time, the dispersion of substances led to the leveling of surface RF bands RF(d1). Syroeshkin et al. / Journal of Applied Pharmaceutical Science 10 (12); 2020: 029-034 033
Figure 5. Two-dimensional (2D) diagrams (“fingerprints”) of 10 descriptors of pharmaceutical substances: L-, D-, and L, D-valine.
The research was not limited to the consideration AUTHORS’ CONTRIBUTIONS of individual descriptors. For a more detailed analysis, a Anton V. Syroeshkin is the author of the new method multidescriptor set was used – a “fingerprint.” It also proved to and contributed to the design of the experiment and theoretical be specific for the optical antipodes of valine and glucose. This is interpretation of experimental results. Olga V. Levitskaya played a reflected in the 2D diagram Fig.( 5). significant role in conducting the experiment and interpreting the Thus, the light scattering patterns of crystals of amino data. Tatiana V. Pleteneva played a leading role in interpreting the acid enantiomers have clear topological differences, which make data and writing this article. Elena V. Uspenskaya and Maria A. it possible to unambiguously identify the L- and D- isomers and Tribot-Laspiere made significant contributions to the writing and final their racemic form. At the same time, the dispersion of crystals of editing of this article. Irina V. Tarabrina made an active contribution pharmaceutical substances led to a pronounced shift and alignment to the acquisition, analysis, and interpretation of data for the article. of the values of all descriptors relative to each other. Further development of the 2D-LS method opens CONFLICT OF INTEREST up prospects for its application for the analysis of the purity The authors declare no conflicts of interest related to the and authenticity of optically active and achiral pharmaceutical publication of this article. substances, as well as their finished dosage forms. FUNDING CONCLUSION This research received no external funding. The use of a mathematical model of folding a 2D-LS pattern into separate descriptors makes it possible to quickly REFERENCES identify compounds that have the same composition and differ Bunkin NF, Shkirin AV, Kozlov VA, Ninham BW, Uspenskaya in spatial structure. Reliability of measurements, nondestructive EV, Gudkov SV. Near-surface structure of Nafion in deuterated water. J nature, low cost, simplicity of calibration procedures, and short Chem Phys, 2018; 149:164901–10. Calcaterra A, D’Acquarica I. The market of chiral drugs: Chiral measurement times are important advantages of the method in the switches versus de novo enantiomerically pure compounds. J Pharm analysis of pharmaceutical substances, including optical antipodes. Biomed, 2018; 147:323–40. Challener C. Expanding the chiral toolbox: recent chiral ABBREVIATIONS advances demonstrate promise for API synthesis. J Pharm Biomed Anal, 2D-LS Two-dimensional light scattering 2016; 40(7):28–9. RF Relative frequency Goncharuk VV, Lapshin VB, Karpov OV, Lesnikov EV, Balakhanov DM, Dan’kin DA, Syroeshkin AV. Nanoparticles in artesian ACKNOWLEDGMENTS waters. J Water Chem Technol, 2011; 33(3):135–9. The publication has been prepared with the support Karpov OV, Balakhanov DM, Lesnikov EV, Dankin DA, Lapshin VB, Paliy AA, Syroeshkin AV, Zagaynov VA. Agranovskii IE. of the “RUDN University Program 5–100,” Moscow, Russian Nanoparticles in ambient air. Measurement methods. Meas Tech, 2011; Federation. 54(3):269–74. 034 Syroeshkin et al. / Journal of Applied Pharmaceutical Science 10 (12); 2020: 029-034
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